Body fat calculator

Type sex, height, neck, and waist. 180 cm, 38 and 90 give about 19.9%. A woman 165/32/65/95 is about 22.4%. Weight is optional and does not enter the %.

Navy formula from girths and height. Not DEXA. Mass BMI lives on the BMI calculator. Resting calories live on BMR.

Input data

Result

Fill in the measurements and click Calculate.

How results are calculated

The US Navy method estimates % BF from girths and height, not from weight. With a metric header you type cm and the formula converts to inches. With a US header you type inches. Men: 86.010×log₁₀(waist−neck) − 70.041×log₁₀(height) + 36.76. 180 cm, neck 38, waist 90: about 19.9%. 175 cm, neck 40, waist 100: about 26.1%.

Women: 163.205×log₁₀(waist+hip−neck) − 97.684×log₁₀(height) − 78.387. 165 cm, neck 32, waist 65, hip 95: about 22.4%. Without hip the women's formula is incomplete. Optional weight turns % into fat and lean mass in kg or lb, but it does not enter the percent.

Pick sex, type height, neck, and waist (and hip for women), then Calculate. The tape should touch, not dig in. Neck under the larynx. Men: navel.

Women: narrowest waist and widest hips. Measure in the morning, the same way each time. 80 kg at the same girths does not change the percent: the formula does not use kilograms.

An estimate usually within about ±3-4 points of a lab, useful for a weekly trend, not a DEXA stand-in. BMI next door divides mass by height squared, with no waist. A high BMI and a narrow waist can read lower here than a lighter person with a large waist. Bands on the result are fitness labels, not a diagnosis.

A man at 170 cm, neck 36, waist 85 reads lower than 180/38/90, because a smaller waist at the same neck lowers the log. A looser tape on the waist raises %. Compare your own sessions week to week. BMR counts rest kcal from Mifflin; here the work stays tape.

How to use

  1. Pick sex. Women get waist at the narrowest point and hips. Men get waist at the navel.
  2. Type height and neck, for example 180 cm and 38 cm.
  3. Type waist. Card example: 90 cm. For women add hips, for example 95 cm at 165 cm height.
  4. Click Calculate. 180 / 38 / 90 give about 19.9%. Weight is optional and does not enter the percent.
  5. Mass-and-height BMI lives on the BMI card. Resting calories live on BMR. Here the work stays Navy tape.

Navy tape and body-fat percent here

Percent comes from girths and height, not from weight. 180 cm, neck 38, waist 90 is about 19.9%; a woman 165/32/65/95 is about 22.4%.

Navy
The US Navy tape method with logs of girths. For a man it uses waist minus neck and height; 80 kg at the same centimeters does not move 19.9%.
BF
Body fat percent from the tape. About 19.9% at 180/38/90 is % BF, not kilograms of fat unless you also type optional weight.
DEXA
A lab scan this calculator does not run. 19.9% from Navy tape is a sketch, often a few points away from a scanner.

Usage examples

Example 1

  • Height: 180 cm, neck: 38 cm
  • Waist: 90 cm, weight: 85 kg

BF ≈ 19.9% - average

A typical result for a moderately fit man.

Example 2

  • Height: 165 cm, neck: 32 cm
  • Waist: 65 cm, hip: 95 cm

BF ≈ 22.4% - fitness

A result within the typical range for active women.

Example 3

  • Height: 175 cm, neck: 40 cm
  • Waist: 100 cm, weight: 98 kg

BF ≈ 26.1% - obese range

A larger waist relative to the neck raises the estimated body fat %.

Example 4

  • Man, height 170 cm, neck 36 cm
  • Waist 85 cm

A smaller waist at the same neck lowers % BF

Weight in the optional field does not change the Navy formula.

Example 5

  • Woman, height 160 cm, neck 31 cm
  • Waist 70 cm, hips 98 cm

Hips are used only for women

Without hips the female Navy formula is missing a girth.

Example 6

  • Man, height 185 cm, neck 39 cm
  • Waist 95 cm

Taller height at a similar waist usually lowers % BF

Still a tape estimate, not DEXA. The weekly trend matters more than one session.

Example 7

  • Woman, height 170 cm, neck 33 cm
  • Waist 78 cm, hips 100 cm

A looser waist tape raises %

Measure in the morning, tape snug not digging in. Otherwise you compare two different measurements.

Related calculators

BMI

BMI calculator: weight and height.

Use calculator →

BMR: basal metabolic rate

BMR calculator: sex, age, weight, and height.

Use calculator →

Protein requirement

Protein requirement calculator: weight and a goal.

Use calculator →

All health calculators

FAQ

What % BF at 180 cm, neck 38, and waist 90?

About 19.9% for a man. The formula takes log of (waist minus neck) and of height. Weight does not enter.

What about a woman 165 / 32 / 65 / 95?

About 22.4%. The log uses waist plus hip minus neck. Without hip the set is incomplete.

Does 80 kg at the same girths change the %?

No. Navy does not use weight. The weight field is for fat and lean mass if you want those kilograms beside the percent.

How should I measure?

Tape touching, not digging. Neck under the larynx. Men: navel. Women: narrowest waist and widest hip. Morning, same method each time.

How accurate is this?

For most people usually ±3-4 points versus a lab. Fine for a trend, not medical precision and not a DEXA stand-in.

Is this the same as BMI?

No. BMI is kg/m² with no girths. A narrow waist at a high BMI can read lower here than a low mass and a large waist.

What do the result categories mean?

Rough fitness bands, not a diagnosis. Compare your own tapes week to week, not a poster label.

What about 170 cm, neck 36, and waist 85?

A smaller waist at the same neck lowers %. Height 185 cm with waist 95 usually pulls % down versus a shorter height.

Does a looser waist tape raise %?

Yes. An extra centimeter at the waist enters the log. A different technique on another day spoils the comparison.

Where are BMI and BMR?

BMI counts mass over height. BMR counts resting kcal from Mifflin. Here the inputs stay girths and height.

Knowledge sources

Body-fat percent uses the US Navy tape method. This is a tape, not a DEXA scan.

Page updated in 2026.